A continuation of research on the catalytic mechanism of the phosphoglucomutase reaction is proposed which includes X-ray diffraction studies on the crystalline enzyme. Judging from the quality of the data thus far collected, this should produce electron density maps with a resolution of 2.7 Angstroms and, together with the amino acid sequence of the enzyme, a model accurate to near atomic resolution. The structure of the active site region of the enzyme and various analog complexes of enzyme-metal-ion-substrate/intermediate/product will be examined to identify the important contact residues. An investigation of the role of co-solutes in the crystal growth process also will be continued in an attempt to improve crystal quality and thus the attainable resolution for active site studies. NMR studies of the relationship between the activating metal ion and the phosphat group that is transferred will be continued in an attempt to determine at what point in the cycle the initial metal-phosphate coordination is eliminated. Kinetic studies are planned to determine whether or not the two dephosphoenzyme-glucose-bisphosphate complexes thought to be involved sequentially in the catalytic cycle are interconverted more rapidly than they are formed or react. Preliminary structural studies on the related phospho-enzyme, gluclose bisphosphate synthase, will be initiated to assess possible similarities to the structure of phosphoglucomutase. Attempts to purify to homogeneity the protein that acts as the zinc buffer in serum will be continued by using muscle phosphoglucomutase to measure zinc-buffering capacity.